Public World APIs for System metadata

## What problem does this solve or what need does it fill?

When using bevy primarily with`run_system_cached`/`run_system_cached_with` (such as server-side turn-based state) you don't have the same level of quality for error reporting as you do in usual Bevy apps as you have access to the SystemId but nothing else – no name for systems that fail to run, so no idea for where to start debugging from.

## What solution would you like?

Some way of accessing system metadata, potentially in a read-only way, using a `World` and a `SystemId` from "the outside" of the bevy internals.

## What alternative(s) have you considered?

Add a "system metadata" field to `RegisteredSystemError`'s variants, as the only reason I want this information is for error reporting.

## Additional context

I'm replacing a "one big state struct" game state with Bevy's ECS, in a context where the ECS is not running continuously but only running based on a given input when there's new events sent to the server. Previous architecture was Client request => Server APIs => call a method on the Big Struct to consume the input from the response, and my current architecture is more or less the same, but with a `World` instead of a Big Struct.

This means I have a number of exclusive systems I run with `run_system_cached` which also might call a bunch of exclusive systems, so there's not a clear understanding of where my errors are propagating from without a function name to match them to.

Start by tracing the public run_system_cached and run_system_cached_with entry points, then inspect RegisteredSystemError and how SystemId values are stored in World. Define what read-only metadata can be exposed outside Bevy internals and how it should support error reporting; the issue is done when the public API and its expected behavior are specified and tested.

Written by the indexing model from the issue text.